Justifying acceptable alternatives to the digital I&C regulatory guides and standards

The NRC expects license amendment requests (LARs) to include an evaluation of the proposed change against the current regulatory criteria; however, it may be difficult to demonstrate compliance to the latest version of regulatory guides (RGs) and endorsed industry standards if the development activities occurred before the current RGs came into effect. Compliance with the regulations is what is required; however, demonstrating compliance to regulations when the associated RGs were not followed can be problematic. As an example development of the complex programmable logic device (CPLD)-based Solid State Protection System (SSPS) cards was started in 2001 and was essentially complete by 2009, but the latest set of Digital instrumentation and control (I&C) RGs became effective in 2013; the CPLD-based SSPS card topical report was docketed for review in February 2014. The single largest challenge with the review of this topical report was demonstrating compliance with the regulations that underlie the Digital I&C RGs. An approach including review of partial compliance to all of the Digital I&C RGs, was tried but ultimately failed because it was not deemed practical to identify each non-conformance to a normative clause and then to explain or justify the alternative for meeting regulatory requirements. The alternative chosen was to evaluate compliance with the regulations, and use the Digital I&C RGs as a guide for the concerns that need to be considered and the appropriate method to adequately addressing each concern. In the end, not all of the concerns are applicable to all applications. In addition, all concerns are presented in the regulatory criteria with equal weight, while in reality some are more important than others. Additionally, it is possible to do more of one activity and less of others and still achieve equivalent level of assurance. This paper presents an alternative approach (i.e., alternative to RGs and endorsed standards) to demonstrating compliance with the regulations that has been shown to work.